1. Technical Field
The present invention relates to an illuminating device, to an electro-optical device, and to an electronic apparatus. In particular, the invention relates to a structure of an illuminating device having a function of controlling light emission of light sources according to detection values of photodetectors.
2. Related Art
In a known illuminating device, light emitted from light sources, such as LEDs, is made incident on a light guide plate, propagates through the light guide plate, and is emitted from a light-emitting surface of the light guide plate. Such an illuminating device has been used as, for example, a planar illuminating device, such as a backlight, for illuminating a liquid crystal panel.
In the illuminating device, uniformity of luminance of light emitted from a light-emitting surface needs to be ensured, and white balance of the emitted light needs to be ensured. Since light sources have variations in luminance and chromaticity, when a plurality of light sources are disposed, a variation in illumination light may be further increased when the individual light sources having different levels of luminance and chromaticity are combined. Therefore, a method of detecting luminance or color tones using photodetectors, which are arranged around the light guide plate or at a light emitting side, and performing feedback control on the luminance and the color tones of the light source according to the detected values has been proposed (for example, see JP-A-2005-91526, JP-A-2004-199968, and JP-A-2005-70132).
However, in the control method using the detection values of the photodetectors, light, which is emitted from the light guide plate, is detected using the photodetectors, and the light sources are controlled on the basis of the detection. For example, devices disclosed in JP-A-2005-91526 and JP-A-2004-199968 detects only light, which is emitted from the light guide plate in a predetermined direction. Therefore, there is a case in which detection values of the photodetectors may not sufficiently reflect the entirety of the illumination light emitted from the light-emitting surface of the light guide plate. Even when the light sources are controlled on the basis of the detection values, the illumination light is not sufficiently controlled.
Further, in a device disclosed in JP-A-2005-70132, in order to detect light incident on a display cell, a photodetector is correspondingly arranged on one substrate surface of the display cell. Therefore, it may not be possible to form only the illuminating device, and a structure of the display cell or a wiring line installation becomes complex, thereby increasing manufacturing costs.